The present exemplary embodiments relate to systems wherein objects are presented, delivered or produced by a plurality of sources and wherein one or more aspects of the presentation, delivery or production of the objects is monitored, measured and/or controlled based on information from a sensor module that is accessible by objects presented, delivered or produced by each of the plurality of object sources. Embodiments will be described in detail in regard to tightly integrated document processing systems. However, embodiments in other object handling or producing systems are also contemplated.
Broadly, document processing systems include input devices, transportation systems and output devices. For example, input devices can include paper trays or drawers. Transportation systems can include conveying devices such as driven nips (spherical or cylindrical), conveyer belts, air jets or vacuums and other mechanisms. Finishing devices can include output trays, staplers, binders, shrink wrappers and bundlers. In the case of printers and copiers, document processors include print engines or integrated marking engines (IMEs).
In copiers and printers, sheets or webs, such as paper or velum are transported by an interposer, or an interposer system, from paper trays or drawers to a print engine or IME. The IME receives data directing the IME to place marks on the delivered sheet. The IME places the marks (e.g., text or an image) on the sheet and the interposer carries the sheet away for further processing or delivery. The interposer may include a reverser for flipping the sheet to present an opposite side for marking. Additionally, or alternatively the interposer may deliver the sheet to an output device, such as an output tray or a finisher.
Some document processors include a plurality of integrated marking engines. Each integrated marking engine (IME) includes sensors and control loops for maintaining or directing one or more IME processes at or toward some ideal or target. For instance, some electro-photographic systems include a hierarchical control scheme. An exemplary electro-photographic system includes level one control loops for maintaining electro-photographic actuators at set points, level two control loops for selecting set points for the level one control loops and level three controls for compensating for residual differences between actual and target values of aspects of the electro-photographic process.
In the case of xerographic systems available actuators can include cleaning field strength or voltage, development field strength or voltage, imager or laser power and an AC wire voltage associated with some developers. For instance, in some xerographic environments, level one control loops include electrostatic volt meters (ESV) for measuring charge voltage generated by charge applied to a photoconductive member. The ESV measure the charge applied in an area of test patches in interdocument or interpage zones (IPZ) of the photo conductor. If measured voltages, such as, for example, a discharge area voltage or a cleaning voltage deviate from set point values, level one control loops adjust these xerographic actuators to return the measured voltage to set point. For example, a charge or bias voltage applied to elements of a developer is adjusted to control a resulting development and/or cleaning field. Additionally, or alternatively, a level one control loop may adjust a laser power to return a related discharge field back toward a discharge field set point.
Level two control loops can include, for example, infrared densitometers (IRD) or enhanced toner area coverage sensors (ETACS) that can measure the density of toner or colorant applied to or developed on a photo conductive member. If the amount of colorant or toner in a test patch is incorrect or varies from a target density, level two control loops generate or select one or more new set points for the actuators of the level one control loops.
Level three control loops may also use IRD or ETACS sensors. The IRD or ETACS sensors sense actual densities of level three test patches associated with a plurality of target level three test patch densities. This provides level three controllers with information about actual tone reproduction curves (TRC) and, therefore, with information about residual error between the actual tone reproduction curve and target tone reproduction curves that could not be addressed by the level two control loops. The level three controls use this information to build color correction look up tables which are used in an image path to alter image data to compensate for the residual error.
Controls such as these can provide excellent quality and consistency within the production of an individual object source. However, differences in sensors, toners or colorants, temperatures, humidities and other parameters and aspects of object sources can lead to variations between objects produced by a first object source and objects produced by a second object source. Variations between the outputs of two or more object sources can be completely acceptable where entire production runs are produced by a single object source. However, when component parts of a single product are produced by different object sources, object source to object source variations can be problematic.
For example, where a document processor includes two or more integrated marking engines, marking engine to marking engine variations can be perceived as consistency or quality issues. For instance, where facing pages in a booklet are rendered by different print engines, slight variations in registration, gray scale or color between the facing pages can be perceived as a defect, even though when considered separately, the pages would be considered to be of high quality.
To combat this perceived quality issue, efforts have been directed toward eliminating IME to IME variations by implementing evermore sophisticated sensors and control algorithms within individual IMEs. However, these solutions are expensive in both research and development costs and hardware implementations delivered to customers. Even where these additional measures are taken, the goal of perfectly matched integrated marking or print engines remains elusive.
Therefore, there is a desire for systems and methods that reduce or eliminate perceived defects due to slight variations in object sources in multi-object source systems.